Difference between revisions of "Ruby/C3/Object-Oriented-Concept-in-Ruby/English-timed"

{| border=1

{| border=1

|| '''Narration'''

|| '''Narration'''

|-

|-

| Welcome to this spoken tutorial on ''' Object Oriented Concept''' in '''Ruby'''.  

| Welcome to this spoken tutorial on ''' Object Oriented Concept''' in '''Ruby'''.  

|-

|-

| In this tutorial we will learn to use-  

| In this tutorial we will learn to use-  

|-

|-

| '''classes'''

| '''classes'''

|-

|-

|creating '''objects'''  

|creating '''objects'''  

|-

|-

|different ways of defining '''methods''' in '''Ruby'''

|different ways of defining '''methods''' in '''Ruby'''

|-

|-

|Here we are using  

|Here we are using  

|-

|-

|  ''' Ubuntu''' version 12.04  

|  ''' Ubuntu''' version 12.04  

|-

|-

|''' Ruby '''1.9.3  

|''' Ruby '''1.9.3  

|-

|-

|To follow this tutorial, you must have knowledge of ''' Linux''' commands, ''' Terminal''' and '''Text-editor.'''

|To follow this tutorial, you must have knowledge of ''' Linux''' commands, ''' Terminal''' and '''Text-editor.'''

    

    

|-

|-

| If not, for relevant tutorials, please visit our website.  

| If not, for relevant tutorials, please visit our website.  

|-

|-

| Before we begin, recall that we had created a ''' “ttt” ''' directory earlier.  

| Before we begin, recall that we had created a ''' “ttt” ''' directory earlier.  

|-

|-

|Let's go to that directory.  

|Let's go to that directory.  

|-

|-

|To ''' ruby hyphen tutorial''' and ''' classes''' directory.  

|To ''' ruby hyphen tutorial''' and ''' classes''' directory.  

|-

|-

|''' Ruby''' is an ''' object oriented''' language.  

|''' Ruby''' is an ''' object oriented''' language.  

|-

|-

| Everything in '''Ruby''' is an object; from a value to a '''string''' or number.  

| Everything in '''Ruby''' is an object; from a value to a '''string''' or number.  

|-

|-

|A '''class''' is a collection of related '''data''' and '''functions.''  

|A '''class''' is a collection of related '''data''' and '''functions.''  

|-

|-

|It can serve to keep information organized.  

|It can serve to keep information organized.  

|-

|-

|An '''object''' is an ''' instantiation''' of a '''class.'''  

|An '''object''' is an ''' instantiation''' of a '''class.'''  

   

   

|-

|-

| A '''class''' definition begins with the keyword '''class.'''  

| A '''class''' definition begins with the keyword '''class.'''  

|-

|-

| It is followed by the name of the '''class.'''  

| It is followed by the name of the '''class.'''  

    

    

|-

|-

| It is delimited with an ''' “end”.'''  

| It is delimited with an ''' “end”.'''  

|-

|-

|Let us look at an example of a ''' class.'''

|Let us look at an example of a ''' class.'''

   

   

|-

|-

|''' class Product'''

|''' class Product'''

|-

|-

|''' ruby code'''  

|''' ruby code'''  

   

   

|-

|-

|'''end'''

|'''end'''

|-

|-

| The name of the '''class''' must begin with a capital letter.  

| The name of the '''class''' must begin with a capital letter.  

|-

|-

|Names that contain more than one word should be camelcased.  

|Names that contain more than one word should be camelcased.  

|-

|-

| For example,  

| For example,  

   

   

|-

|-

| ''' UserInformation'''

| ''' UserInformation'''

|-

|-

| '''ProductInformation'''

| '''ProductInformation'''

|-

|-

|The subsequent file names will have underscore separating the words:  

|The subsequent file names will have underscore separating the words:  

|-

|-

|''' user underscore information'''  

|''' user underscore information'''  

|-

|-

|''' product underscore information'''  

|''' product underscore information'''  

|-

|-

| Create a new file in ''' gedit''' as shown in the basic level '''Ruby''' tutorials.  

| Create a new file in ''' gedit''' as shown in the basic level '''Ruby''' tutorials.  

|-

|-

| Name it ''' class_definition.rb'''

| Name it ''' class_definition.rb'''

|-

|-

| I have a working example of the implementation of '''classes.'''

| I have a working example of the implementation of '''classes.'''

|-

|-

|You can pause the tutorial, and type the code as we go through it.  

|You can pause the tutorial, and type the code as we go through it.  

|-

|-

| I have defined a ''' class''' named ''' Order''' in this example.  

| I have defined a ''' class''' named ''' Order''' in this example.  

|-

|-

| Now let us make the ''' class''' useful by adding some '''variables.'''  

| Now let us make the ''' class''' useful by adding some '''variables.'''  

|-

|-

|Then I have defined an ''' instance variable “myinstance”.'''

|Then I have defined an ''' instance variable “myinstance”.'''

|-

|-

|And I have assigned a value to it.  

|And I have assigned a value to it.  

|-

|-

|I have also defined a ''' class variable “myclassvar” '''

|I have also defined a ''' class variable “myclassvar” '''

|-

|-

|And I have assigned a value to it.  

|And I have assigned a value to it.  

|-

|-

|Now let us add some code that will make use of this class.  

|Now let us add some code that will make use of this class.  

|-

|-

| Type ''' puts Order dot instance underscore variables.'''

| Type ''' puts Order dot instance underscore variables.'''

|-

|-

| Before this line, add '''puts''' some characters '''slash n''' for a new line.  

| Before this line, add '''puts''' some characters '''slash n''' for a new line.  

|-

|-

| Let us copy and paste that and add it just below the line we added and save it.  

| Let us copy and paste that and add it just below the line we added and save it.  

|-

|-

| Now let us execute this code

| Now let us execute this code

|-

|-

|Switch to the terminal and type  

|Switch to the terminal and type  

|-

|-

| ''' ruby space class underscore definition dot rb'''  

| ''' ruby space class underscore definition dot rb'''  

   

   

|-

|-

|and see the output.  

|and see the output.  

|-

|-

| You will see the ''' instance variable''' you defined.

| You will see the ''' instance variable''' you defined.

|-

|-

|Now let us type ''' puts Order dot class underscore variables.'''  

|Now let us type ''' puts Order dot class underscore variables.'''  

|-

|-

|Let us copy and paste the demarcation, just below the line and save it.  

|Let us copy and paste the demarcation, just below the line and save it.  

|-

|-

| Now let us switch to the '''terminal''' and execute the file like before.   

| Now let us switch to the '''terminal''' and execute the file like before.   

|-

|-

|You will notice the ''' class variable''' you defined, also show up.  

|You will notice the ''' class variable''' you defined, also show up.  

|-

|-

| To now be able to write your own '''class.'''

| To now be able to write your own '''class.'''

|-

|-

|  Next, let us look at what an '''object''' is.   

|  Next, let us look at what an '''object''' is.   

|-

|-

|An '''object''' is an '''instance''' of a '''class.'''

|An '''object''' is an '''instance''' of a '''class.'''

|-

|-

| Which means an '''object''' is created from a '''class.'''  

| Which means an '''object''' is created from a '''class.'''  

|-

|-

|An '''object''' will have the properties and '''methods''' defined in the '''class.'''  

|An '''object''' will have the properties and '''methods''' defined in the '''class.'''  

|-

|-

| How do you declare an '''object'''

| How do you declare an '''object'''

|-

|-

|We declare an '''object''' of a class using the '''new keyword.'''  

|We declare an '''object''' of a class using the '''new keyword.'''  

    

    

|-

|-

|Here we are declaring an '''object''' of the '''Product class.'''  

|Here we are declaring an '''object''' of the '''Product class.'''  

|-

|-

| Here an '''object''' gets created.  

| Here an '''object''' gets created.  

|-

|-

|''' product = Product.new'''  

|''' product = Product.new'''  

|-

|-

| This process is called ''' initialization''' of an object.  

| This process is called ''' initialization''' of an object.  

|-

|-

|This '''object''' is of '''type''': '''Product.'''  

|This '''object''' is of '''type''': '''Product.'''  

|-

|-

|Now let is look at what an ''' “initialize” method''' is.  

|Now let is look at what an ''' “initialize” method''' is.  

|-

|-

|An ''' initialize method''' is called at the time of '''object''' creation.  

|An ''' initialize method''' is called at the time of '''object''' creation.  

|-

|-

| On calling '''new''' on an '''object''', we invoke the '''initialize method.'''  

| On calling '''new''' on an '''object''', we invoke the '''initialize method.'''  

|-

|-

|An '''initialize method''' may take a list of '''parameters.'''   

|An '''initialize method''' may take a list of '''parameters.'''   

|-

|-

|Like other ''' Ruby methods''', it is preceded by the ''' “def” keyword.'''

|Like other ''' Ruby methods''', it is preceded by the ''' “def” keyword.'''

|-

|-

|Let us look at an example.  

|Let us look at an example.  

|-

|-

|Create a new file in '''gedit''' as shown in the basic level '''Ruby''' tutorials.  

|Create a new file in '''gedit''' as shown in the basic level '''Ruby''' tutorials.  

|-

|-

| And name it '''object undescore initialize dot rb '''

| And name it '''object undescore initialize dot rb '''

|-

|-

| I have a working example of the ''' object initialization''' code.  

| I have a working example of the ''' object initialization''' code.  

|-

|-

| You can pause the tutorial, and type the code as we go through it.   

| You can pause the tutorial, and type the code as we go through it.   

|-

|-

|Here I have defined a ''' class''' called ''' “Order” '''

|Here I have defined a ''' class''' called ''' “Order” '''

|-

|-

|Then I have defined the ''' initialize method''', with no '''argument.'''

|Then I have defined the ''' initialize method''', with no '''argument.'''

|-

|-

| I have defined a '''puts method''' to display the message '''“I have created an object”.

| I have defined a '''puts method''' to display the message '''“I have created an object”.

|-

|-

|Next, I have defined '''Order dot new'''.

|Next, I have defined '''Order dot new'''.

|-

|-

|This will invoke the '''initialize method.'''  

|This will invoke the '''initialize method.'''  

|-

|-

|Switch to the '''terminal''' and type  

|Switch to the '''terminal''' and type  

   

   

|-

|-

|'''ruby space object underscore initialize dot rb'''  

|'''ruby space object underscore initialize dot rb'''  

|-

|-

| and see the output.  

| and see the output.  

|-

|-

|You will see the message ''' “I have created an object” ''' .  

|You will see the message ''' “I have created an object” ''' .  

|-

|-

|Now let us go back to '''gedit''' and add an '''argument''' to the '''method.'''

|Now let us go back to '''gedit''' and add an '''argument''' to the '''method.'''

|-

|-

|Let us modify the ''' puts''' .   

|Let us modify the ''' puts''' .   

|-

|-

|It should display the value of the ''' argument''' passed.  

|It should display the value of the ''' argument''' passed.  

|-

|-

| Next let us type  

| Next let us type  

|-

|-

|''' Order dot new(“I have created an object”). '''

|''' Order dot new(“I have created an object”). '''

|-

|-

|Here we have given an argument to the new method.  

|Here we have given an argument to the new method.  

|-

|-

| This '''argument''' gets passed on to the '''initialize method.'''  

| This '''argument''' gets passed on to the '''initialize method.'''  

   

   

|-

|-

|Switch to the ''' terminal''' and type  

|Switch to the ''' terminal''' and type  

|-

|-

|''' ruby space object underscore initialize dot rb'''  

|''' ruby space object underscore initialize dot rb'''  

|-

|-

|and see the output.  

|and see the output.  

|-

|-

|You will see the message ''' “I have created an object” ''' printed out.  

|You will see the message ''' “I have created an object” ''' printed out.  

   

   

|-

|-

| Now, you would have understood what ''' object initialization''' means.  

| Now, you would have understood what ''' object initialization''' means.  

|-

|-

|Recall that in '''Ruby, methods''' are the '''functions''' that a '''class''' performs.  

|Recall that in '''Ruby, methods''' are the '''functions''' that a '''class''' performs.  

|-

|-

|Each '''method''' in a class is defined within the ''' “def” '''  and ''' “end”''' block.  

|Each '''method''' in a class is defined within the ''' “def” '''  and ''' “end”''' block.  

|-

|-

|A multiword ''' method'''  name is separated with an '''underscore.'''

|A multiword ''' method'''  name is separated with an '''underscore.'''

|-

|-

|Some of the characters that can be appended to a '''method''' name are:   

|Some of the characters that can be appended to a '''method''' name are:   

|-

|-

|''' ? (question-mark) '''

|''' ? (question-mark) '''

|-

|-

|''' = (equal to) '''  

|''' = (equal to) '''  

|-

|-

|Each of the characters add some meaning to the '''method.'''  

|Each of the characters add some meaning to the '''method.'''  

|-

|-

|Let us look at some examples.  

|Let us look at some examples.  

   

   

|-

|-

|Create a new file in ''' gedit''' as shown in the basic level '''Ruby''' tutorials.  

|Create a new file in ''' gedit''' as shown in the basic level '''Ruby''' tutorials.  

|-

|-

|And name it ''' class underscore methods dot rb'''.

|And name it ''' class underscore methods dot rb'''.

|-

|-

|I have a working example of ''' class methods''' code.  

|I have a working example of ''' class methods''' code.  

|-

|-

|You can pause the tutorial, and type the code as we go through it.   

|You can pause the tutorial, and type the code as we go through it.   

|-

|-

|Here I have defined a class named ''' “Animal”.'''

|Here I have defined a class named ''' “Animal”.'''

|-

|-

|Then I have two ''' methods “breathe” ''' and ''' “walk”.'''

|Then I have two ''' methods “breathe” ''' and ''' “walk”.'''

|-

|-

|They are both defined with the ''' “def” ''' and ''' “end”''' keywords.  

|They are both defined with the ''' “def” ''' and ''' “end”''' keywords.  

|-

|-

|I have then initialized the ''' object Animal.'''

|I have then initialized the ''' object Animal.'''

|-

|-

|I have assigned it to a variable called  ''' “animal”''' with lowercase ''' “a”.'''  

|I have assigned it to a variable called  ''' “animal”''' with lowercase ''' “a”.'''  

|-

|-

|Then I have invoked the ''' methods “breathe” ''' and ''' “walk” ''' consequtively.  

|Then I have invoked the ''' methods “breathe” ''' and ''' “walk” ''' consequtively.  

|-

|-

|Now let us execute the program.  

|Now let us execute the program.  

|-

|-

|Switch to the '''terminal''' and type  

|Switch to the '''terminal''' and type  

|-

|-

|''' ruby space class underscore methods dot rb '''

|''' ruby space class underscore methods dot rb '''

|-

|-

|and see the output.  

|and see the output.  

|-

|-

|You will notice the lines:  

|You will notice the lines:  

|-

|-

|'''“ I breathe”  '''

|'''“ I breathe”  '''

|-

|-

|'''“ I walk” '''

|'''“ I walk” '''

|-

|-

|printed out.  

|printed out.  

|-

|-

|This is because you have invoked the two methods ''' “breathe” ''' and ''' “walk”. '''

|This is because you have invoked the two methods ''' “breathe” ''' and ''' “walk”. '''

|-

|-

|A '''“puts” ''' statement defined within these '''methods''' gives the results you see.  

|A '''“puts” ''' statement defined within these '''methods''' gives the results you see.  

|-

|-

|Next, let us look at how to create '''methods''' with a trailing '''question mark.'''

|Next, let us look at how to create '''methods''' with a trailing '''question mark.'''

|-

|-

|Create a new file in '''gedit''' as shown in the basic level Ruby tutorials.  

|Create a new file in '''gedit''' as shown in the basic level Ruby tutorials.  

|-

|-

|And name it '''class underscore methods underscore with underscore trailing underscore characters dot rb'''

|And name it '''class underscore methods underscore with underscore trailing underscore characters dot rb'''

|-

|-

|I have a working example of '''class methods''' with '''question mark''' code.  

|I have a working example of '''class methods''' with '''question mark''' code.  

|-

|-

|You can pause the tutorial, and type the code as we go through it.  

|You can pause the tutorial, and type the code as we go through it.  

|-

|-

|Here I have taken the same class as before as an example.  

|Here I have taken the same class as before as an example.  

|-

|-

|Here the '''breathe method''' has a trailing '''“question mark (?)”. '''

|Here the '''breathe method''' has a trailing '''“question mark (?)”. '''

|-

|-

|Such '''methods''' are generally used to return '''boolean values. '''

|Such '''methods''' are generally used to return '''boolean values. '''

|-

|-

|This is based on the '''method''' naming convention of Ruby.  

|This is based on the '''method''' naming convention of Ruby.  

|-

|-

|The '''method''' gets invoked by declaring '''animal dot breathe question-mark'''

|The '''method''' gets invoked by declaring '''animal dot breathe question-mark'''

|-

|-

|Switch to the '''terminal''' and type  

|Switch to the '''terminal''' and type  

|-

|-

|'''ruby space class underscore methods underscore with underscore trailing underscore characters dot rb'''  and see the output.  

|'''ruby space class underscore methods underscore with underscore trailing underscore characters dot rb'''  and see the output.  

|-

|-

|You will notice the output as :  ''' “true” '''

|You will notice the output as :  ''' “true” '''

|-

|-

|Next, let us define another '''method''' called '''“walk”.'''

|Next, let us define another '''method''' called '''“walk”.'''

|-

|-

|Let us place an ''' equal-to''' sign ''' “=(value)”''' beside it.  

|Let us place an ''' equal-to''' sign ''' “=(value)”''' beside it.  

|-

|-

|Let us invoke this ''' method''' by calling ''' animal dot walk.'''  

|Let us invoke this ''' method''' by calling ''' animal dot walk.'''  

|-

|-

|Then let us execute this '''method. '''

|Then let us execute this '''method. '''

|-

|-

|Switch to the '''terminal''' and type  

|Switch to the '''terminal''' and type  

|-

|-

|'''ruby class underscore methods underscore with underscore trailing underscore characters dot rb '''

|'''ruby class underscore methods underscore with underscore trailing underscore characters dot rb '''

|-

|-

|and see the output.  

|and see the output.  

|-

|-

|It will give an ''' “undefined method” ''' error.  

|It will give an ''' “undefined method” ''' error.  

|-

|-

|This is because the ''' equal to sign''' has another meaning.  

|This is because the ''' equal to sign''' has another meaning.  

|-

|-

|It is used to assign a value to a ''' method.'''

|It is used to assign a value to a ''' method.'''

|-

|-

|So, let us invoke the '''method''' a little differently this time.  

|So, let us invoke the '''method''' a little differently this time.  

|-

|-

|Type '''puts animal dot walk equal to “ hops” '''

|Type '''puts animal dot walk equal to “ hops” '''

|-

|-

|Now let give it another try.  

|Now let give it another try.  

|-

|-

|Switch to the ''' terminal''' and run the command like before and see the output.  

|Switch to the ''' terminal''' and run the command like before and see the output.  

|-

|-

|You will notice that the word  '''“hops”''' get printed.  

|You will notice that the word  '''“hops”''' get printed.  

|-

|-

|This demonstrates that the ''' equal to sign''' next to a method means assignment.

|This demonstrates that the ''' equal to sign''' next to a method means assignment.

|-

|-

|Now you should be able to write your own '''methods. '''

|Now you should be able to write your own '''methods. '''

|-

|-

|In this tutorial we have learnt-  

|In this tutorial we have learnt-  

|-

|-

|How to declare '''classes '''

|How to declare '''classes '''

|-

|-

|How to create ''' objects''' of a ''' class '''

|How to create ''' objects''' of a ''' class '''

|-

|-

|Different ways of defining '''methods''' in '''Ruby'''  

|Different ways of defining '''methods''' in '''Ruby'''  

|-

|-

|As an assignment:  

|As an assignment:  

|-

|-

|Define a '''class Product '''

|Define a '''class Product '''

|-

|-

|Define '''methods''' that you can use to get values of “myvar” and set values for “myvar”.  

|Define '''methods''' that you can use to get values of “myvar” and set values for “myvar”.  

|-

|-

|To set values, define the '''method''' using “=” sign.  

|To set values, define the '''method''' using “=” sign.  

|-

|-

|Instantiate the object of the class and set and get values using the above 2 methods.  

|Instantiate the object of the class and set and get values using the above 2 methods.  

|-

|-

|  Watch the video available at the following link.

|  Watch the video available at the following link.

|-

|-

|It summarises the Spoken Tutorial project.

|It summarises the Spoken Tutorial project.

|-

|-

|If you do not have good bandwidth, you can download and  watch it.  

|If you do not have good bandwidth, you can download and  watch it.  

|-

|-

|  The Spoken Tutorial Project Team :

|  The Spoken Tutorial Project Team :

|-   

|-   

|Conducts workshops using spoken tutorials  

|Conducts workshops using spoken tutorials  

|-

|-

|Gives certificates to those who pass an online test  

|Gives certificates to those who pass an online test  

|-

|-

|For more details, please write to contact@spoken-tutorial.org

|For more details, please write to contact@spoken-tutorial.org

|-

|-

|  Spoken Tutorial Project is a part of the Talk to a Teacher project.

|  Spoken Tutorial Project is a part of the Talk to a Teacher project.

|-

|-

|It is supported by the National Mission on Education through ICT, MHRD, Government of India.

|It is supported by the National Mission on Education through ICT, MHRD, Government of India.

|-

|-

|More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro

|More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro

|-

|-

| This is Anjana Nair signing off. Thank you

| This is Anjana Nair signing off. Thank you

|}

|}